Update:  I have now added an HDMI splitter.  So, final confirguration is:

Video:
T-Box --> HDMI cable --> HDMI Splitter -->
HDMI cable x 2 -one output to TV, one output to HDFury2 -->
Component (YPbPr) cables --> HD PVR -->
USB Cable --> Home Theatre PC.

Audio:
T-Box --> optical cable --> HD PVR

All works absolutely brilliantly.

The ArcSoft Total Media Extreme (TME) software which comes bundled with the HD PVR is mediocre.  There doesn't seem to be any ability to schedule a recording.  So I record on T-Box, set it playing then in TME set the duration and click capture.  Once recorded on the PC I use Video ReDo to trim out anything I don't want.  This is preferable to my other video editing applications because they all require rendering and Video ReDo doesn't. All working in time for the Tour de France.  Yay!

Anything broadcast on Freeview I record directly to the PC using the inbuilt Freeview card and just trim with Video ReDo.    But for content only available through the cable service, the rather long winded process described above is painful but effective.

I am still a little surprised at how difficult it was to find out how to get all this to work.  I mean, doesn't everyone with a T-Box, My Sky box or equivalent want to do this?  It's very frustrating to have something recorded on the box but not be able to edit it or burn it to DVD.  I guess we are still pioneering.